This invention relates to a new process for preparing organic sulphides, and more specifically for preparing aliphatic, aromatic, arylaliphatic and heterocyclic thioethers.
Thioethers are known industrially to constitute a large class of products used in many fields, for example as dyestuff and pharmaceutical intermediates, as pesticides, herbicides, oxidation inhibitors, additives for load-bearing lubricants and the like.
Because of the importance of this class of product, numerous processes have been proposed up to the present time for its preparation, these however being generally limited to the preparation of alkyl thioethers.
The most widely used industrial processes known up to the present day comprise:
1. Reacting an alkyl halide with a thiol in accordance with the equation: EQU R--X+YS--R.sub.1 .fwdarw.R--S--R.sub.1 +XY
in which R is an alkyl group, R.sub.1 is an aliphatic, aryl, arylaliphatic or heterocyclic radical, X is halogen, and Y is H or an alkali metal. According to one alternative the alkyl halide can be replaced by an alkyl sulphate; or
2. Reacting an alkyl mercaptan with an organic halide in accordance with the equation: EQU R--SH+X--R.sub.1 .fwdarw.R--S--R.sub.1 +HX
in which R is an alkyl group, R.sub.1 is an aliphatic, aryl, arylaliphatic or heterocyclic radical, and X is halogen.
Reaction (1) is generally used for preparing dialkyl sulphides or alkylaryl sulphides, whereas reaction (2) is most commonly used for preparing alkyl sulphides of heterocyclic compounds. Obviously, said reactions are carried out under very different operating conditions according to the specific reactants involved. In many cases, and in particular when R.sub.1 is a heterocyclic radical, rather drastic temperature and pressure conditions and very long times are necessary. In addition, those processes which use alkyl mercaptans suffer from all the drawbacks which the use of such toxic and volatile compounds involves.
The present invention relates to a new extremely simple and economical process, which allows the industrial preparation, with high yields, in very short times and in the absence of solvents, of thioethers of formula: EQU R--S--R.sub.1
in which R is an aliphatic, aryl, arylaliphatic or heterocyclic radical and R.sub.1 is an aliphatic or arylaliphatic radical.
The process is of general character, and can be used for preparing practically any thioether included in the aforesaid formula, under substantially equivalent conditions.